Native gold in complex Ti-Zr placers of the southern West Siberian Plain

摘要

Typomorphic features of native gold and its contents in complex Ti-Zr placers in the southern West Siberian Plain are reported. Three of the placers are of littoral-marine genesis, and two formed under conditions of an alluvial piedmont plain. Native gold from the studied Ti-Zr placers occurs mainly as flattened thin (-0.1 mm) particles which underwent mechanical action. It is marked by wide fineness variation and the abundance of a very fine (990-1000‰) variety. Most likely, this is chemically transformed clastogenic metal. The gold content of the productive bed (5-30 mg/m~3 native gold and 8-140 ppb bulk gold) is consistent with the dispersion of heavy ore and accessory minerals during mechanical migration in water flows simultaneously with their concentration on geochemical barriers. The native-gold content of complex Ti-Zr placers shows a higher negative correlation with the primary source-placer distance than those of Ti and Zr minerals and a positive correlation with the degree of hydrodynamic reworking (gravity concentration) of transit terrigenous material. On the southern framing of the West Siberian Plain, some regions of northern Kazakhstan are promising for gold of complex Ti-Zr placers as well as fine- and thin-gold placers, gold-bearing weathering crusts, and primary gold deposits.